0:14Skip to 0 minutes and 14 secondsIt's a great pleasure to introduce you to my colleague and good friend, John Bishop. John, you're a philosopher of religion. Can you tell us what philosophy of religion is about? Well, one thing philosophers of religion are very interested in is whether it's justifiable for people to commit themselves to the truth of their religious beliefs. And many philosophers would say that that's only justifiable if they've got good reasons for them. And in order to have good reasons, they should have arguments which show that their religious beliefs are true. And of course, when we apply this to the religions that are founded on belief in God, it's all about arguments for and against God's existence.

0:57Skip to 0 minutes and 57 secondsOK, so then how does the distinction between deductive and non-deductive arguments play out in this kind of context? Well, we find arguments of both types. Perhaps I can illustrate that, first of all by thinking about arguments for God's existence. Now, one argument is called the cosmological argument. And there's a version of it that's recently been revived from mediaeval Islamic theology by the American philosopher, William Lane Craig. It's called the Kalam cosmological argument. And it's possible to state it very easily in standard form. It goes like this-- everything that begins to exist has a cause of its existence. The universe began to exist. Therefore, the universe has a cause of its existence.

1:52Skip to 1 minute and 52 secondsSo what kind of challenge might one propose against this argument? Well, given that it's a deductive argument, one might question whether it really is the case that everything-- literally everything that begins to exist has a cause of its existence. Possibly that applies only to things within the universe and not to the universe itself. So that's one possible challenge. Another possible challenge might be to say, well, yes, I think the argument does succeed. But does it really establish the existence of God? The cause of the universe is something tremendous, but it does it have to be God? And actually, that gives me an opportunity to bring in a non-deductive argument, which is known as the fine-tuning argument.

2:39Skip to 2 minutes and 39 secondsThe fundamental physical constants of the universe are within a very narrow range that is required if the universe is going to be capable of supporting life. The best explanation for this phenomenon is that those values were set by an intelligence who was acting for a purpose that required the existence of life. And therefore, given that that is the best explanation, it is probably true that the universe has an intelligent designer. OK, and because it's a non-deductive argument, it leaves out the possibility that God may not exist, I suppose. Because it's a non-deductive argument, it doesn't guarantee that God exists, because it allows us to say that it might, perhaps, be an amazing coincidence-- a matter of chance.

3:44Skip to 3 minutes and 44 secondsAnd that is not ruled out by the argument. So that raises the question, are there are arguments against the existence of God? Yes, there certainly are. And we can find examples amongst those kinds of arguments as the difference between deductive and non-deductive arguments. Now, one very common argument against the existence of God is the argument from evil. And it goes like this-- if God exists, God is both all powerful and perfectly good. If God is all powerful, God is able to prevent any evil he wishes to prevent. If God is perfectly good, God wishes to prevent any evil he can prevent. Therefore, if God has both those properties, there is no evil. But we know from experience that evil exists.

4:44Skip to 4 minutes and 44 secondsHence, it follows that God does not exist. Theists, of course, theist philosophers have objected to this argument by saying it doesn't succeed, because it leaves out the possibility that God may be prepared to cause or permit some forms of evil in order to achieve really important goods that would not be achievable otherwise. But that puts into doubt the deductive version for the argument from evil. That's right. So the atheist philosophers, however, responded by saying, If an all-powerful and perfectly good God exists, there are no pointless evils. Probably, there are pointless evils. Therefore, probably there is no all-powerful and perfectly good God. We can find plenty of instances of evil which seem to be pointless. Like what?

5:49Skip to 5 minutes and 49 secondsAn example comes from an article by William Rowe that has been much discussed, is of a fawn who's caught in a forest fire and is badly burned, but takes a long time to die in agony over several days from these burns. And certainly, when we consider an evil like that, it seems inconceivable to us that it could have any purpose or point that might justify it. Now, of course, we can't absolutely rule out the possibility that it has some completely unknown purpose to us. It's just on the basis of what we know, it's very probable that it doesn't.

6:29Skip to 6 minutes and 29 secondsAnd that, then, gives us reason for saying that very probably, there are pointless evils, and therefore, very probably, a God who, if he existed would prevent pointless evils, doesn't exist. OK, so you've given us examples in the philosophy of religion for arguments both for the existence of God and against the existence of God. And for each kind of arguments, we had deductive and non-deductive arguments. But I suppose it's not only for deep questions like the existence of God that the distinction is important. Is that right? I think that is right.

7:08Skip to 7 minutes and 8 secondsI mean, what we've seen in philosophy of religion is that it's important for people to think carefully about what they're trying to achieve with their arguments, whether they're attempting to provide an argument strong enough to guarantee the conclusion, or whether what they're trying to do is provide premises that will make it cogent to think that the conclusion is probably, or highly probably, true. And I agree with you. I think that's something that people ought to consider in many different contexts, not just in philosophy of religion.

Arguments for and against the existence of God

In this video, John Bishop and Patrick discuss various arguments for and against the existence of God, with an emphasis on the distinction between deductive and non-deductive arguments.